5-Series (E12,E28, E34, E39, E60)Chat relating to the BMW 5-Series of all generations. Specific models include: BMW 518, BMW 520, BMW 520i, BMW 530i, BMW 528i, BMW 530i, BMW 518i, BMW 524d, BMW 525i, BMW 525e, BMW 528e, BMW 540i, BMW 535i, BMW 520d, BMW 525td, BMW 525d, BMW 530d, BMW 525i/xi, BMW 530i/xi. (BMW 5-Series Forum)
I have a 1984 533i that is not holding idel. Once warn the engine goes into the strange cycle where it revs up to 1700 rpm and then back down to 1000 rpm and just keep going, back and forth as if it's searching for a corect idel rate. I can't afford to have a mechanic work on it. I know how to fix things, but this puzzels me to no end. any pointers from you BMW guys? I think it's vacuume related.
could be several things. What makes you think it's vacuum related? Did something occur to make you think so? It could certainly be vacuum related. I would check over all of your vacuum hoses and connections along with all of the intake ducting. As mentioned, I would also try cleaing your Idle air control valve. While it is idling and doing the surging, try tapping on the IAC with the handle of a good sized screwdriver. Sometimes those guys will stick and after a couple whacks, they will settle down. There is always a chance you could have an ECU problem and there could be other issues. Go with the easiest and obvious first.
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I do not believe that this is an ECU problem. It is your idle control valve or a vaccum line that goes to it. Check the vaccum lines that go to that valve. If they are in good shape, take out the valve and spray carb cleaner in it and shake it well. you should hear a ball moving back and forth. This is good. spray a little WD-40 in it and shake it up. Re-install it. Also there is a screw in the valve that you can use to adjust the idle. If this does not work, you will need a new valve. They are not cheap!
If you need an idle valve,you may also find the idle conrl unit defective, Just cut it all out and install the factory euro idle control system for under 150.00. that will eliminate theentire foolishness of electronics controlling the idle. Then you will havenice simple mechanical devices contolling the idle,justa s BMW AG intended. I have done this on several at my shop and sold numerous others over the years
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